The heart is a hollow muscular organ having four pumping chambers separated by four heart valves: aortic, mitral (or bicuspid), tricuspid, and pulmonary. Heart valves are comprised of a dense fibrous ring known as the annulus, and leaflets or cusps attached to the annulus.
Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. In a traditional valve replacement operation, the damaged leaflets are typically excised and the annulus sculpted to receive a replacement prosthetic valve.
In tissue-type valves, a whole xenograft valve (e.g., porcine) or a plurality of xenograft leaflets (e.g., bovine pericardium) can provide fluid occluding surfaces. Synthetic leaflets have been proposed, and thus the term “flexible leaflet valve” refers to both natural and artificial “tissue-type” valves. In a typical tissue-type valve, two or more flexible leaflets are mounted within a peripheral support structure that usually includes posts or commissures extending in the outflow direction to mimic natural fibrous commissures in the native annulus. The metallic or polymeric “support frame,” sometimes called a “wireform” or “stent,” has a plurality (typically three) of large radius cusps supporting the cusp region of the flexible leaflets (e.g., either a whole xenograft valve or three separate leaflets). The ends of each pair of adjacent cusps converge somewhat asymptotically to form upstanding commissures that terminate in tips, each extending in the opposite direction as the arcuate cusps and having a relatively smaller radius. Components of the valve are usually assembled with one or more biocompatible fabric (e.g., polyester, for example, Dacron® polyethylene terephthalate (PET)) coverings, and a fabric-covered sewing ring is provided on the inflow end of the peripheral support structure.
Sometimes the need for complete valve replacement may arise after a patient has already had an earlier valve replacement for the same valve. For example, a prosthetic heart valve that was successfully implanted to replace a native valve may itself suffer damage and/or wear and tear many years after initially being implanted. Implanting the prosthetic heart valve directly within a previously-implanted prosthetic heart valve may be impractical, in part because the new prosthetic heart valve (including the support structure and valve assembly) will have to reside within the annulus of the previously-implanted heart valve, and traditional prosthetic heart valves may not be configured to easily receive such a valve-within-a-valve implantation in a manner that provides secure seating for the new valve while also having a large enough annulus within the new valve to support proper blood flow therethrough.
Some attention has been paid to the problem of implanting a new valve within an old valve. In particular, the following disclose various solutions for valve-in-valve systems: U.S. Patent Application Publication No. 2010/0076548, filed Sep. 19, 2008; U.S. Pat. No. 8,613,765, filed Jul. 7, 2011; and International Publication No. WO 2012/018779, filed Aug. 2, 2011. The entire disclosures of these publications are expressly incorporated herein by reference.
Despite certain advances in the valve-in-valve area, there remains a need for a prosthetic heart valve that facilitates the process while maximizing the life of the first valve and simplifying manufacturing techniques.